1. Field of the Invention
The present invention relates to a thermal processing apparatus for thermally processing a semiconductor wafer or a glass substrate (hereinafter simply referred to as “substrate”) by irradiating the same with light.
2. Description of the Background Art
In general, a thermal processing apparatus such as a lamp annealing apparatus using a halogen lamp is employed in an ion activation step for an ion-implanted semiconductor wafer. This thermal processing apparatus heats (anneals) the semiconductor wafer to a temperature of about 1000° C. to 1100° C., for example, thereby carrying out the ion activation step for the semiconductor wafer. This thermal processing apparatus increases the temperature of the substrate at a rate of about hundreds of degrees per second through the energy of light emitted from the halogen lamp.
However, it has been proved that the profile of ions implanted into the semiconductor wafer is rounded, i.e., the ions are thermally diffused when the ion activation step is carried out with the thermal processing apparatus heating the substrate at the rate of about hundreds of degrees per second. If this phenomenon takes place, the ions implanted into the surface of the semiconductor wafer are diffused also when the same are implanted in high concentration. Therefore, the ions must disadvantageously be implanted beyond necessity.
In order to solve the aforementioned problem, there is proposed a technique of irradiating the surface of a semiconductor wafer with flash light through xenon flash lamps or the like thereby increasing the temperature of only the surface of the ion-implanted semiconductor wafer in an extremely short time of not more than several milliseconds. When heating the semiconductor wafer with the xenon flash lamps for an extremely short time, the ions are not diffused due to a shortage of time and hence only the ion activation step can be carried out without rounding the profile of the ions implanted into the semiconductor wafer.
Such a thermal processing apparatus using xenon flash lamps is generally formed by fitting a lamp house comprising the xenon flash lamps and a chamber storing and holding the semiconductor wafer to each other in an openable/closable manner through a hinge. The aforementioned fitted structure is closed when the thermal processing apparatus flash-heats the semiconductor wafer, and opened when the apparatus is subjected to maintenance.
In general, however, an operator may carelessly come into contact with any of the xenon flash lamps provided in the lamp house to break this lamp during maintenance of the apparatus. The xenon flash lamps are high-priced, and much time is disadvantageously required not only for exchanging the lamp but also for re-adjusting the overall lamp house if any of the xenon flash lamps is broken.